1. Field of the Invention
The present invention relates to digital image data (hereafter, called simply xe2x80x9cimage dataxe2x80x9d) compression and/or reconstruction method, apparatus and a storage medium thereof. The xe2x80x9cimage data compressionxe2x80x9d is defined as the process of decreasing the amount of image data, whereas the xe2x80x9cimage data reconstructionxe2x80x9d is defined as the process of putting it back to the original amount of image data, which is the amount before the data was decreased.
2. Description of the Related Art
In recent years, the demand for transmitting and receiving image data via communication lines have increased as communication networks such as internets are developed and expanded. In systems for simply transmitting and receiving image data, there is a situation where: it is impossible to display image data on the receiver side until its reception has been completed; or even if the image data has been successfully displayed on the receiver side because it displays parts of the image data in the order of receiving them, it is difficult to determine whether or not the image data to be displayed on the receiver side is necessary.
Accordingly, in order to improve this situation, the following techniques for holding multiple resolutions of image information aligned in a hierarchical structure and transmitting the image information step by step: FlashPix (which is the trademark owned by Eastman Kodak Company) and Progressive JPEG have been proposed.
However, there are problems with those conventional techniques where the transmission of each stage of image data causes an increase in the total amount of transmission data and/or the desired amount of each stage of transmitting data cannot be designated.
The present invention has been developed taking the above problems into consideration. Its objective is to provide an apparatus and method for transmitting image data at multi-levels without an increase in the total amount of data to be transmitted, and a storage medium thereof.
Further, an objective of the present invention is to provide an apparatus, a method and its storage medium for designating the amount of data to be transmitted at each level.
According to an aspect of the present invention, an image compression apparatus that compresses m pixels of first image data into n (n less than m) pixels of second image data is provided. This image compression apparatus is comprised of an image data compressor that: multiplies neighboring pixels in the said first image data by respective given coefficients, which are set up so that sum of the said given coefficients can be equal to a value resulting from division of m by n; sums up the resultant values obtained by the multiplication; and multiplies the resultant summed value by a value resulting from division of n by m, into the resulting value which functions as a value of a pixel in the said second image data.
According to another aspect of the present invention, an image reconstruction apparatus, which reconstructs first image data from the second image data including n (n less than m) pixels that results from compressing the said first pixel data including m pixels, is provided. This image reconstruction apparatus is comprised of an image data reconstructor that calculates a pixel value in the said first image data from pixels in the said second image data and reconstruction pixel values that have been picked out from the said first image data.
According to still another aspect of the present invention, an image compression method, which compresses m pixels of first image data into n (n less than m) pixels of second image data, is provided. This method is comprised of the process of multiplying of neighboring pixels in the said first image data by respective given coefficients, which are set up so that sum of the said given coefficients can be equal to a value resulting from division of m by n, summing up the resultant values obtained by the multiplication, and multiplying the resultant summed value by a value resulting from division of n by m, into the resulting value which functions as a value of a pixel in the said second image data.
According to still another aspect of the present invention, an image reconstruction method that reconstructs first image data from second image data including n (n less than m) pixels, which results from compressing the said first image data including m pixels, is provided. This image reconstruction method is comprised of the process of calculating a pixel value in the said first image data from both a pixel value in the said second image data and a reconstruction pixel value picked out from the said first image data.
According to still another aspect of the present invention, a storage medium that is stored with a computer program for compressing m pixels of first image data into n (n less than m) pixels of second image data is provided. The said computer program enables a computer to execute: a step of multiplying neighboring pixels in the said first image data by respective given coefficients, which are set up so that sum of the said given coefficients can be equal to a value resulting from division of m by n; a step of summing up the resultant values obtained by the multiplication; and a step of multiplying the resultant summed value by a value resulting from division of n by m, into the resulting value which functions as a value of a pixel in the said second image data.
According to still another aspect of the present invention, a storage medium that is stored with a computer program for reconstructing first image data from second image data including n (n less than m) pixels, which results from compressing the said first image data including m pixels, is provided. The said computer program enables a computer to execute: a step of calculating a pixel value in the said first image data from both a pixel value in the said second image data and a reconstruction pixel value picked out from the said first image data.